Britain may have to undertake military operations sooner than people think because of the rapidly changing security situation around the world, the head of the Army said.

Gen Sir Peter Wall said Britain now faced a growing range of threats, from attack by ballistic missiles, to terrorism and cyber warfare.

The Chief of the General Staff also repeated warnings that any further defence cuts after the 2015 election would endanger the Army’s new slimmed down structure.

Sir Peter told the Royal United Services Institute (RUSI) that: “We must pay special attention to understanding the rapidly shifting environment in which we may well have to operate sooner than some would have us think.”

There was currently little public appetite in the UK for foreign military operations, “but that could soon change”, he said.

He called for defence spending to increase as the economy rebounds and said beleaguered plans to offset the loss of regular troops with part-time reserves must work soon or be scrapped altogether.

Sir Peter said the Army reforms were complicated and had “plenty of risk”.

He also predicted that the Army would increasingly be called on to help out in domestic crises.

“Homeland operations are growing and the Land Forces command and control model and regional networks have been well tested by floods, potential fuel tanker driver strikes, and striking firemen," he said.